1. Field of the Invention
The present invention relates to tools and equipment used in carpentry and related fields. More specifically, the present invention comprises a chalk box and chalk line used for marking guidelines on construction materials and other surfaces. The chalk box may include an electric motor for rewinding the chalk line after use, and may include a line clip having a spring-biased line clip that can be released from an anchor without manual intervention.
2. Description of the Related Art
Chalk lines have been in common use for laying out straight lines for cutting, nailing, etc. on construction materials, for a considerable time. The basic process involves coating or impregnating a pervious string or line with chalk dust, stretching the line taut along the surface to be marked, and snapping the taut line against the surface. The chalk dust, which is shaken from the line as it impacts the surface, instantly marks a straight line along the surface of the material being marked.
Various containers, or “chalk boxes,” have been developed to store such chalk lines. In its simplest form, such a container comprises an open reel upon which the chalk line is wound. More complex devices have been developed, in which the chalk line is wound upon a closed reel by an external crank. Many such devices include a reservoir or compartment for containing chalk dust to automatically impregnate or coat the chalk line with dust as the line passes therethrough, and may include means for removing excessive dust as the line passes from the reel or box.
Still other chalk boxes have been developed which include a coil spring that biases the reel to retract the line after use. While this facilitates the rewinding of the chalk line, the force of the coil spring generally results in relatively rapid retraction of the chalk line into the housing or box, if the retraction speed is unchecked. This can result in the line clip at the end of the chalk line, flailing about and potentially causing injury.
The present inventors are aware of certain spring-powered devices developed in the past for the purpose of rewinding a cord or line. An example of such is found in Japanese Patent Publication No. 55-052,865 published on Apr. 17, 1980. This patent publication discloses (according to the drawings and English abstract) an electric cord reel having a cam actuated release mechanism to allow the cord to be retracted onto the reel without locking up the reel rotation.
Another spring wound device is found in Japanese Patent Publication No. 63-082,302, published on Apr. 13, 1988. This device comprises (according to the drawings and English abstract) a spring-wound rope or line, which is used for measuring a distance or span. The distance may be determined according to the spring travel within the device, with an electronic sensor and optical pickup determining the spring travel.
A small number of mechanized chalk boxes have been developed which utilize an electric motor to rewind the chalk line after use. This results in a somewhat slower and more uniform retraction speed for the line, which provides a safer operation of the retraction process. However, most such devices are relatively bulky due to the location of the electric motor relative to the chalk line reel and remaining components.
Regardless of the principle used to rewind the chalk line, all such devices include some means of temporarily holding or securing the distal end of the chalk line to the opposite side of the range to be marked. Such line clips generally include a slot that may be hooked over the protruding head or end of a nail or screw, and a bend which may be hooked over the edge or end of a panel, wall stud, etc. Such devices are generally easily removed once the line is marked, but also generally require a second person at the opposite end of the chalk line to remove the clip when it is installed over a screw or nail. This is not a major problem when working on a floor or similar surface, as the person controlling the chalk box need only walk to the opposite end of the line to unhook the clip himself. However, the task becomes somewhat more involved when working on a narrow scaffold or between stories, etc. The assistance of a second person in such circumstances is practically essential, in order to avoid the need to continually move up and down ladders, climb and descend scaffolding, etc.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus, a motorized chalk box solving the aforementioned problems is desired.